Dash deployment on webfaction problem

I want to deploy my dash product on my webfaction server. I followed the tutorial suggest me to delpoy a falsk app. I’ve successfully done that. The index.py is

import os
import sys

CURRENT_FILE = os.path.abspath(__file__)
CURRENT_DIR = os.path.dirname(CURRENT_FILE)
PROJECT_DIR = os.path.dirname(CURRENT_DIR)

# Add project top-dir to path (since it has no __init__.py)
sys.path.append(PROJECT_DIR + '/src/')

# Add virtualenv to path
sys.path.append(PROJECT_DIR + '/virtualenv/lib/python3.7/site-packages/')

# Export the Flask app object from the project as wsgi application object
from myapp0 import server as application

the myapp0.py is

from flask import Flask
app = Flask(__name__)

def hello():
    return "Hello World!"

if __name__ == "__main__":

It works fine but and I change the flask hello world test content to dash test content in the tutorial. To deal with the errors, I add


my new myapp0.py is

import os

import dash
import dash_core_components as dcc
import dash_html_components as html

external_stylesheets = ['https://codepen.io/chriddyp/pen/bWLwgP.css']

app = dash.Dash(__name__, external_stylesheets=external_stylesheets,app.scripts.config.serve_locally=True)

server = app.server

app.layout = html.Div([
    html.H2('Hello World'),
        options=[{'label': i, 'value': i} for i in ['LA', 'NYC', 'MTL']],

@app.callback(dash.dependencies.Output('display-value', 'children'),
              [dash.dependencies.Input('dropdown', 'value')])
def display_value(value):
    return 'You have selected "{}"'.format(value)

if __name__ == '__main__':

this test code comes from tutorial on dash websitehttps://dash.plot.ly/deployment

I change the content of the file, such as making

    html.H2('Hello World'),


    html.H2('Hello World asd'),

but it does’t work. I delete cache, and change a browser, but things don’t change neither.
Could anyone please help? Thank you so much.